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1// SPDX-License-Identifier: GPL-2.0-only2/* ----------------------------------------------------------------------- *3 *4 * Copyright 2012 Intel Corporation; author H. Peter Anvin5 *6 * ----------------------------------------------------------------------- */7 8/*9 * earlycpio.c10 *11 * Find a specific cpio member; must precede any compressed content.12 * This is used to locate data items in the initramfs used by the13 * kernel itself during early boot (before the main initramfs is14 * decompressed.) It is the responsibility of the initramfs creator15 * to ensure that these items are uncompressed at the head of the16 * blob. Depending on the boot loader or package tool that may be a17 * separate file or part of the same file.18 */19 20#include <linux/earlycpio.h>21#include <linux/kernel.h>22#include <linux/string.h>23 24enum cpio_fields {25 C_MAGIC,26 C_INO,27 C_MODE,28 C_UID,29 C_GID,30 C_NLINK,31 C_MTIME,32 C_FILESIZE,33 C_MAJ,34 C_MIN,35 C_RMAJ,36 C_RMIN,37 C_NAMESIZE,38 C_CHKSUM,39 C_NFIELDS40};41 42/**43 * find_cpio_data - Search for files in an uncompressed cpio44 * @path: The directory to search for, including a slash at the end45 * @data: Pointer to the cpio archive or a header inside46 * @len: Remaining length of the cpio based on data pointer47 * @nextoff: When a matching file is found, this is the offset from the48 * beginning of the cpio to the beginning of the next file, not the49 * matching file itself. It can be used to iterate through the cpio50 * to find all files inside of a directory path.51 *52 * Return: &struct cpio_data containing the address, length and53 * filename (with the directory path cut off) of the found file.54 * If you search for a filename and not for files in a directory,55 * pass the absolute path of the filename in the cpio and make sure56 * the match returned an empty filename string.57 */58 59struct cpio_data find_cpio_data(const char *path, void *data,60 size_t len, long *nextoff)61{62 const size_t cpio_header_len = 8*C_NFIELDS - 2;63 struct cpio_data cd = { NULL, 0, "" };64 const char *p, *dptr, *nptr;65 unsigned int ch[C_NFIELDS], *chp, v;66 unsigned char c, x;67 size_t mypathsize = strlen(path);68 int i, j;69 70 p = data;71 72 while (len > cpio_header_len) {73 if (!*p) {74 /* All cpio headers need to be 4-byte aligned */75 p += 4;76 len -= 4;77 continue;78 }79 80 j = 6; /* The magic field is only 6 characters */81 chp = ch;82 for (i = C_NFIELDS; i; i--) {83 v = 0;84 while (j--) {85 v <<= 4;86 c = *p++;87 88 x = c - '0';89 if (x < 10) {90 v += x;91 continue;92 }93 94 x = (c | 0x20) - 'a';95 if (x < 6) {96 v += x + 10;97 continue;98 }99 100 goto quit; /* Invalid hexadecimal */101 }102 *chp++ = v;103 j = 8; /* All other fields are 8 characters */104 }105 106 if ((ch[C_MAGIC] - 0x070701) > 1)107 goto quit; /* Invalid magic */108 109 len -= cpio_header_len;110 111 dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);112 nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);113 114 if (nptr > p + len || dptr < p || nptr < dptr)115 goto quit; /* Buffer overrun */116 117 if ((ch[C_MODE] & 0170000) == 0100000 &&118 ch[C_NAMESIZE] >= mypathsize &&119 !memcmp(p, path, mypathsize)) {120 121 if (nextoff)122 *nextoff = (long)nptr - (long)data;123 124 if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {125 pr_warn(126 "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",127 p, MAX_CPIO_FILE_NAME);128 }129 strscpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);130 131 cd.data = (void *)dptr;132 cd.size = ch[C_FILESIZE];133 return cd; /* Found it! */134 }135 len -= (nptr - p);136 p = nptr;137 }138 139quit:140 return cd;141}142